Metal bellows, or flexible metal convoluted tubing, has provided a conventional means of connecting piping systems usually one of which tends to be a stationary system to other systems which are subjected to various types of movement. Particularly, the metal bellows have found considerable use in piping sytems utilizing a or other equipment which can transfer vibratory and other movements to a piping system. Piping systems, subject to substantial temperature differences, systems subject to pressure differences and systems which require sound deading connectors have utilized flexible connectors. A metal bellows, which is subjected to a torsional loading, usually has premature ring-like failure around one or more of the metal convolutes. This premature failure is directly related to the torsional loading, the loci stresses, and thus is an inherent disadvantage of flexible metal bellows. Repetitive torsional loading will initiate a much earlier failure in such bellows. The stress centers from this torsional loading are located generally through a combination of geometrical considerations, thickness of metal, resident stress, and other minor unconformities which when added to the motion and resonance centers, collectively, make individual identification and prediction of stress location uneconomical, if possible at all. The lack of axial alignment in many cases causes metal bellows to sustain early failure because of the concentration of stresses in the areas of convergence and divergence of the bellows undergoing flexing.
A characteristic of metal bellows seems to be that the thinner the web or metal of the bellows, the greater the flexibility and longer life during flexure. However, as a corollary of this, as the metal is made thinner the greater the vulnerability to crushing of the inner convolute from increased pressures, and of course, subsequent early failures.